The Total Yeast and Mold (TYM) test for Cannabis gives an indication of the level of contamination of Cannabis by yeast and mold. As with total bacterial tests, tests for “total yeast and mold” are essentially a quality test. They are unlikely to serve as a good indicator for the presence of pathogens. In fact, the typical agar plates used to assess total yeast and mold levels are able to support the growth of only a very tiny percentage of the fungal species common in the environment. However, yeasts and molds can cause total deterioration of the Cannabis if it is not properly stored. Also certain species of mold, such as Aspergillus flavus, produce toxins (aflatoxins) that can potentially cause diseases such as cancer.
Why Test Cannabis for Total Yeasts and Molds
There are two rationales for requiring such a test for Cannabis. The first is that since mold is so common on Cannabis, and high levels are likely as a result of many different environmental and processing factors (harvest timing, seasonal rain levels, curing processes, cross contamination, etc), it makes sense to include a total yeast and mold test as a general quality indicator. The other rationale is that, even though such tests do not serve as indicators for the potential presence of pathogens, mold is a potential cause of irritation and allergic hypersensitivity reactions.
It is important to note that total yeast and mold (TYM) test does not determine the presence or absence of pathogenic or toxin producing molds, making this test a poor indicator of potential health risk.